Glycemic control in insulin dependent diabetes mellitus (T1D) is improved with the administration of the lacking hormone, insulin. However, the euglycemic window is very narrow, and administration of exogenous insulin poses the risk of hypoglycemia. This is aggravated by the fact that the mechanism that the body uses to restore euglycemia from a hypoglycemic state no longer works properly in T1D. The secretion of glucagon, another hormone produced in the endocrine part of the pancreas, fails to increase when blood glucose deceases below the hypoglycemic threshold. In general, the mechanisms that regulate the secretion of glucagon are only partially known. It is known that glucagon secretion is associated with a decrease in blood glucose, but whether only glucose can regulate glucagon secretion from the pancreatic alpha cell (alpha cell) is a matter of controversy. It was found that glutamate is an endogenous stimulus that amplifies glucagon release from the alpha cell when blood glucose decreases. It was previously proposed that glutamate, which like glucagon is also released from the alpha cell, forms an autocrine positive feedback loop to regulate glucagon release. The long term goal of this research is to define the signaling pathways involved in the regulation of glucagon release from the alpha cell in order to identify molecular targets that can be used as therapeutic sites to treat hypoglycemia in diabetes. This application hypothesizes that a change in glutamate signaling in the pancreatic islets (islets) contributes to the failure of glucose counter-regulation in T1D. To test this hypothesis, the following aims are proposed: (a) establish a model of T1D to study glutamate-induced glucagon release in vitro, (b) make use of this model to investigate the molecular mechanism by which glutamate amplifies glucagon release, and (c) use insulin dependent diabetic mice to determine the contribution of glutamate to glucose counter-regulation in an environment of T1D. To accomplish the above aims, the following experiments will be conducted: (1) stimulate with glutamate isolated islets devoid of beta cells and cultured in high glucose to determine glutamate-induced glucagon release in an T1D-like environment, (2) investigate the signaling properties of the glutamate receptors present in the alpha cell, and (3) apply a hyperinsulinemic-hypoglycemic clamp to insulin dependent diabetic mice to determine the contribution of glutamate to glucose counter-regulation. A conceptually novel hypothesis is proposed to determine the relevance of glutamate receptors in the alpha cell to glucose counter-regulation. This research has the potential to provide clues of how to utilize glutamate receptors in the endocrine pancreas to treat hypoglycemia in T1D.